Near-infrared disguise detection

ABSTRACT

Detection of a person disguised with one or more artificial materials includes detecting reflection from at least one portion of a head of a human body in at least a portion of an upper band of the near infrared spectrum. The presence of an artificial material associated with the head of the human body is determined based on the detected reflection.

BACKGROUND OF THE INVENTION

[0001] The present invention pertains to detection systems and methods.More particularly, the present invention pertains to detection systemsand methods using the near-infrared spectrum for the detection of, forexample, disguised persons.

[0002] In certain situations, disguise detection is of paramountimportance. For example, in high-end security applications, e.g.,surveillance of an embassy perimeter where there is a need to know ifdisguised terrorists are staking out a facility, disguise detection isrequired. Sophisticated systems for early detection and identificationof individuals at a distance need to be developed and implemented forfuture security systems.

[0003] Sophisticated terrorists use both natural (e.g., darkness,weather, blending into the background) and man-made (e.g., heavymake-up, artificial face parts, add-on hair, etc.) deception anddisguise techniques to avoid identification. Currently, systems that candetermine whether an individual is wearing a facial disguise arelacking. Therefore, face identification processes and systems that havethe capability to identify a particular human face cannot even beinitiated, or even if such processes are initiated, the processes do notknow of the possible disguise being used by the individual. Therefore,the face identification processes are easily rendered ineffective. Assuch, the mere detection of a disguised individual on the perimeter ishighly valuable to security forces.

[0004] One article entitled “Disguise detection and identification usinginfrared imagery,” by F. J. Prokoski, Proceedings of SPIE, Optics, andImages in Law Enforcement II, A. S. Hecht, Ed., Arlington, pp. 27-31,Virginia, May 1982, describes a disguise detection system that usesfacial thermograms in the thermal infrared spectrum for the detection ofdisguises and in positive identification of known individuals. However,thermal infrared radiation does not transmit effectively through glass,e.g., so as to allow for detection of disguises within vehicles.

[0005] Other portions of the spectrum are also ineffective for use indisguise detection. For example, even though the visible spectrum hasbeen used in imaging and detecting individuals, such visible spectrumsystems or methods are not effective for disguise detection. Disguisescannot be detected in the visible band because by definition suchdisguises are meant to cheat the human eye and the other sensors thatoperate in the same wavelength. In other words, in the visible spectrum,artificial materials disguising an individual are not detectable.

[0006] Further, for example, the lower portion of the electromagneticspectrum consists of gamma rays, x-rays, and radiation in theultra-violet range. Radiation of such wavelengths is harmful. Thus, suchradiation that is typically useful in a controlled manner, e.g., formedical applications, cannot generally be used for disguise detection.

[0007] At the far end of the electromagnetic spectrum, there ismicrowave and radio radiation. This range of the spectrum has recentlystarted to be exploited for imaging purposes. Sensors operate in anactive or in passive mode. The major advantage of such longerwavelengths is that they can penetrate clouds, fog, and rain forproducing weather independent imaging results. However, the technologyfor such wavelengths is new and prohibitively expensive. Also, thesensors available for detection in this range of radiation are extremelylarge and have very low resolution.

[0008] Related efforts by others, for example, in the field of detectingoccupants in vehicles, such as for gathering statistics in highoccupancy vehicle lanes which can be used for road constructionplanning, have involved the use of a near-infrared camera (i.e., in therange of 0.55 to 0.90 micron) and a near-infrared illumination source inthe same range of wavelengths. One reason for using near-infraredsensing is the ability to use non-distracting illumination at night.Illumination at nighttime enhances the quality of the image. However, itappears that this choice of range of wavelengths is not appropriatebecause of its close proximity to the visible spectrum. Experiments haveshown that the human eye has some sensitivity to this range ofnear-infrared wavelengths, however small. Another reason for thisapproach, was to bypass problems caused by solar illumination duringdaytime, such as glare from glass of vehicles. Nevertheless,particularly in this range of the spectrum (i.e., 0.55 to 0.9 micron)solar illumination is still substantial and the associated glare can bereduced only through the use of polarizing filters.

[0009] Further, in more general terms, related art projects that involveimaging usually adopt the use of visible spectrum cameras which asdescribed above, are ineffective in disguise detection. One strong pointof the visible spectrum is that the relevant imaging sensors are veryadvanced and at the same time very economical. Visible spectrum camerashave a particular advantage in terms of speed, which is an importantconsideration, for example, in detecting occupants in vehicles, wherevehicles are moving at rates of speed of 65 mph. These cameras can alsohave very high resolution, resulting in very clear images under variousconditions. However, unfortunately, in addition to not detectingdisguised individuals, there are other serious problems with the visiblespectrum approach. For instance, some vehicles have heavily tintedwindow glass to reduce glare from solar illumination. This glass isnearly opaque to visible spectrum cameras. Also, visible spectrumcameras do not have operational capability during nighttime.

[0010] Visible spectrum or very near infrared detection of people invehicles has not been very successful under most conditions. The glareand other problems caused by solar illumination, such as through vehiclewindows, has prevented effective detection of vehicle occupants. Also,environmental conditions like weather obscure detection. People appearto have darker or lighter faces, depending on the characteristics of thepeople being detected, and on the incident angle and intensity ofdeliberate or incidental illumination.

SUMMARY OF THE INVENTION

[0011] Various embodiments of the present invention provide solutions toone or more problems existing with respect to detection systems andmethods, and in particular disguise detection systems and methods. Suchembodiments may provide one or more of the following advantages. Forexample, disguised faces may be detected within vehicles through windowglass thereof. Further, the present invention provides a simplethresholding system that can deliver excellent disguise detectionresults. In addition, the existence of specific materials used fordisguise purposes may be identified.

[0012] The present invention capitalizes on the unique and universalproperties of the natural human skin and/or natural human hair in theupper band of the near-infrared spectrum. Some embodiments of themethods according to the present invention include one or more of thefollowing: detecting reflection from at least one portion of a head of ahuman body in at least a portion of an upper band of the near-infraredspectrum (e.g., at least a portion within the range of 1.4 μm andgreater in the upper band of the near-infrared spectrum); determiningthe presence of an artificial material associated with the head of thehuman body based on the detected reflection; detecting reflection fromat least a skin portion of the head of the human body; detectingreflection from at least a hair portion of the head of the human body;determining the presence of an artificial material associated with thehead of the human body by displaying to a user a representation of thedetected reflection; determining the presence of an artificial materialassociated with the head by generating data representative of thedetected reflection and comparing the data to at least one thresholdreference reflection level; identifying one or more artificial materialsassociated with the head; basing the threshold reference reflectionlevel(s) on a level of reflection of natural skin of the human body, thelevel of reflection of natural hair of the human body, or the level ofreflection of one or more artificial materials; using an illuminationsource matched to the upper band of the near-infrared spectrum detectedto illuminate the head of the human body; controlling the illuminationsource based on a detected illumination level to maintain the desiredillumination level on the head of the human body.

[0013] Some embodiments of a disguised person detection system includeone or more of the following features: a detector apparatus operable todetect reflection from at least a portion of the head of the human bodyin at least a portion of an upper band of the near-infrared spectrum; anindication apparatus operable to provide a user with information as tothe presence of an artificial material associated with the head of thehuman body based on the detected reflection (e.g., wherein theindication apparatus comprises a display operable to provide arepresentation of the detected reflection and/or wherein the indicationapparatus may comprise circuitry operable to compare informationrepresentative of the deflected reflection to one or more thresholdreference reflection levels, wherein the threshold reference reflectionlevels may be based on a level of reflection of one or more artificialmaterials, the natural skin of the human body, the natural hair of thehuman body, etc.); an illumination source matched to the at least aportion of the upper band of the near-infrared spectrum and positionedto illuminate at least a portion of the head of the human body; adetector operable to detect an illumination level proximate the head soas to provide information to circuitry operable to control theillumination source based on the detected illumination level such that adesired illumination level can be maintained.

[0014] Further, in other embodiments of the present invention, adetection method may include detecting reflection from a scene in atleast a portion of at least one band of the near-infrared spectrum, andthereafter, determining the presence of a head of the human body in thescene. The features of the disguise detection methods and/or systemdescribed above may then be used to determine the presence of anartificial material associated with the detected head.

[0015] The above summary of the present invention is not intended todescribe each embodiment or every implementation of the presentinvention. Advantages, together with a more complete understanding ofthe invention, will become apparent and appreciated by referring to thefollowing detailed description and claims taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE EMBODIMENTS

[0016]FIG. 1 shows a near-infrared fusion system for detecting humans.

[0017]FIG. 2A illustrates a co-registration scheme for two cameras.

[0018]FIG. 2B shows an alternate embodiment for co-registration of thecameras.

[0019]FIG. 3 is a histogram of the number of pixels versus spectralpower for an image frame.

[0020]FIG. 4 is a graph of the electromagnetic (EM) spectrum.

[0021]FIG. 5 reveals the infrared transmittance characteristics for anautomobile windshield.

[0022]FIG. 6 reveals the infrared transmittance characteristics for anautomobile side window.

[0023]FIG. 7 is a graph showing the percentage of reflectance forCaucasian males of light and dark complexions.

[0024]FIG. 8 is a graph showing the percentage of reflectance for Asianmales of light and dark complexions.

[0025]FIG. 9 is a graph showing the percentage of reflectance for blackmales of light and dark complexions.

[0026]FIG. 10 is a graph showing a comparison of reflectance for lightand dark skin.

[0027]FIG. 11 is a graph of reflectance for cotton, wood and polyamide.

[0028]FIG. 12 is a graph of reflectance for distilled water.

[0029]FIG. 13 shows a layout for determining the speed characteristicsof a human detection system.

[0030] FIGS. 14A-B shows the appearance of an undisguised individual inthe visible spectrum and in the upper band of the near-infraredspectrum, respectively.

[0031] FIGS. 15A-B show the appearance of a disguised individual in thevisible spectrum and in the upper band of the near-infrared spectrum,respectively.

[0032]FIG. 16 shows one illustrative embodiment of a disguise detectionsystem according to the present invention.

[0033]FIG. 17 is a graph of reflectance for natural human hair.

[0034]FIG. 18 is a graph of reflectance for a true human hair toupee.

[0035]FIG. 19 is an illustrative embodiment of one disguise detectionmethod according to the present invention.

[0036]FIG. 20 is yet another alternate embodiment of a disguisedetection method according to the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037]FIG. 1 shows a basic layout of a near-infrared fusion system 10for detecting humans. It is a dual-band imaging system. Twoco-registered cameras 11 and 12 sense the image of, for instance, a face13 of a human being. Camera 11 has a spectral sensitivity of 0.8 to 1.4microns. Camera 12 has a spectral sensitivity of 1.4 to 2.2 microns.Slightly shorter or longer ranges can also yield acceptable detectionresults. The 1.4 micron threshold point between the two bands ofspectral sensitivity is a preferable demarcation point for the dual-bandsystem 10, but may be another value as appropriate. Each of the camerasensitivity band ranges can cross somewhat the 1.4 micron wavelengthwithout diminishing the human detecting ability of system 10.

[0038] The quality of the imaging signals from cameras 11 and 12 remainhigh even during overcast days and at nighttime, because the scene beingscanned by cameras 11 and 12, can be illuminated with an eye-safenear-infrared illuminator 14. Since the eye is not sensitive to thenear-infrared spectrum, system 10 can remain stealthy all of the time,whether in a detection mode or not. Ideally, the camera at the lowerband range (0.8 to 1.4 microns) should be an image intensifier.Therefore, the illuminator's spectral emission specification needs tomatch only with the upper band range (1.4 to 2.2 microns). The upperband range is quite far from the visible spectrum and illumination inthese wavelengths is safe even for highway applications. Near-infraredcameras 11 and 12 provide clear imaging signals even in foul weatherconditions such as hazy conditions. These particular infrared bands ofdetection and illumination provide for sufficient light transmissionthrough windshields, side windows, fog, and darkness. This permitsadequate detection of humans in vehicles at night and in poor weather.

[0039] The image outputs 15 and 16 of cameras 11 and 12, respectively,go to a weighted difference software process 17 or specialized hardwarethat fuses the outputs by performing weighted subtraction of theintensities of the two camera images. This weighted difference softwareor hardware may be referred to as a fuser. Such fusion of the cameraoutputs intensifies the silhouette of face 13 and other exposed humanskin in the resultant fused image. Also, the image features a diminutionof the background of the scene being covered by the cameras. Thisincreased contrast between the person and the background in the fusedimage permits essentially perfect image segmentation throughthresholding by a software process 18, or specialized hardware. Thisthresholding software or hardware may be referred to as a thresholder.The output of the thresholder 18 may go to a display 19, printer, or apost-process or specialized hardware.

[0040] A final processed image shows the exposed skin parts, such asface 13, as binary blob 13′, as shown in FIG. 1. Background 20 of sensedface 13 is discounted as shown by blank background 20′ in display 19.This clean-cut binary imagery ensures reliable and fast operation of apattern recognition algorithm that identifies a human as indicated byface 13′ imagery.

[0041]FIG. 2A illustrates the co-registration of cameras 11 and 12.There is spatial and time registration between the cameras. The camerascould be of the same make and model. The necessary difference betweenthe cameras is the optical bandwidth filters, 48 and 49, which aresituated between sensing arrays 46 and 47 and camera lens 58 and 59,respectively, of cameras 11 and 12. Filter 48 determines the 0.8 to 1.4micron spectral sensitivity of array 46 in camera 11 and filter 49determines the 1.4 to 2.2 micron spectral sensitivity of array 47 incamera 12. A polarizer may be inserted in front of lens 58 of camera 11and in front of lens 59 of camera 12. Or instead, a polarizer may beinserted between lens 58 and array 46 of camera 11, and between lens 59and array 47 of camera 12. Sensing arrays 46 and 47 of the cameras arethe same size, for example, 512 by 512 pixels in a gallium arsenidesubstrate. Typically, the fields of view are the same for each array.Three pixels 51, 52, and 53, for example, are selected out for spatialco-registration. Each of the three pixels are focused on correspondingportions 51′, 52′, and 53′, respectively, of image 20 viewed by cameras11 and 12. That means the arrays have the same images, pixel for pixel,even though the spectral sensitivities are different. In other words,the columns and rows of pixels are aligned with the physical worldscene, pixel for pixel. Once spatially co-registered, cameras 11 and 12are kept stationary relative to the physical world.

[0042] Time co-registration of the cameras means that the cameras are insynchronization with each other from a signal perspective. The signalsfor each of the two corresponding pixels go to a frame buffer at thesame time. The retention of light for each pixel is in the micro-secondrange. A typical frame time is about 33 milliseconds, which is 30 framesper second. The transfer of pixel data may be parallel, line-by-line, orserial, pixel-by-pixel, or any other style of information transfer.There is a sync signal for cameras 11 and 12 to initiate and maintaintheir time co-registration.

[0043] The image outputs or pixel signals 15 and 16 go to a softwareprocess or specialized hardware 17 which provides a certain weighting toeach of the pixels and fuses pairs of corresponding pixels from cameras11 and 12, respectively, into single pixels. The weighted differencingis performed pixel by pixel. Each result is the fused pixel of the twoweighted differenced pixels. The weight difference equation for suchfusing is

P(i,j)_(fused) =P(i,j)_(lower band) −C*P(i,j)_(upper band*)

[0044] P is spectral power. The position or location of each pixel inthe respective image is identified by row (i.e., “i”) and column (i.e.,“j”). The rows and columns of pixels of the images of cameras 11 and 12coincide with each other. The lower band pixels are those from camera 11and the upper band pixels are those from camera 12. The spectral power“P” for each pixel at i,j is indicated, for example, by a numeral scaleof brightness from 0 to 255 for 8-bit resolution. “0” is entirely blackor dark (i.e., no spectral power) and “255” is entirely white or bright(i.e., full spectral power). Numerical indications in between 0 and 255are, of course, representative of various gradations of gray,brightness, or spectral power. “C” of the equation is a constant (i.e.,weighting factor), which is determined according to the lighting ofbackground or scene 20 and object or face 13. “C” for daytime lightingconditions is about 3 for optimal results. “C” for nighttime dependsupon the spectral distribution and properties of an artificialilluminator 14.

[0045] The brightness or spectral power of a typical pixel of the lowerband (image 46) may be 55 and the brightness or spectral power of thecorresponding typical pixel of the upper band (image 47) may be 10.These upper and lower band pixel values are representative of skin inthe corresponding bands. The spectral power of a resulting typical fusedpixel, in daytime viewing, at a location of row i and column j in thedaytime is determined with the following calculation.

P(i,j)_(fused)=55−3*10

P(i,j)_(fused)=55−30=25

[0046] The fused pixel signals go from software process or specializedhardware 17 to software process or specialized hardware 18 for imagesegmentation via thresholding of the fused pixels. Process orspecialized hardware 18 emulates a comparator-like circuit in that eachfused pixel below a certain threshold value (T) is assigned a value (V₁)of 0 and each fused pixel above the certain threshold value is assigneda value (V₂) of 255.

[0047]FIG. 3 shows a histogram of an image frame of fused pixels. Thenumber of pixels for each spectral power value is indicated by curves 54and 55 for a given sensed image. The pixels of curve 54 representbackground 20 and the pixels of curve 55 represent human skin 13. Curves54 and 55 intersect at 56 that is deemed to be the appropriate value forthresholding. If curves 54 and 55 do not intersect, then thethresholding value 56 is centered between curves 54 and 55. Thethreshold value is dynamic in that it changes from frame to frame, andis determined for each image frame according to the histogram of therespective frame. If the spectral value for thresholding is 20, thenfused pixels having a value below 20 are valued at 0 and fused pixelshaving a value above 20 are valued at 255. The resulting image indisplay 19 has white pixels for background 20′ and black pixels for face13′. This image may be reversed by process or specialized hardware 18such that background 20′ has black pixels and face 13′ has white pixels.

[0048]FIG. 2B shows an alternate embodiment for co-registration of thecameras 11 and 12. As shown therein, an optical device 57, e.g., abeamsplitter/filter device, is used to provide co-registration of thecameras. The setup is essentially the same as that shown in FIG. 2A,except that the filters 47, 48 are not provided with the cameras 11 and12. Instead, filtering is provided by the optical device 57.

[0049] As shown in FIG. 2B, light comes from the environment through thebeamsplitter/filter optical device 57 to the two near infrared cameras11 and 12 as represented by the points of light 51-53. Thebeamsplitter/filter optical device 57 is an optical device with acoating that performs optimally at a specific angle. Thebeamsplitter/filter optical device 57 directs light with wavelengthsbelow 1.4 microns (i.e., the lower band) to camera 11 and light withwavelengths above 1.4 microns (i.e., upper band) to the other camera 12.The cameras 11, 12 are preferably connected to a computer for processingvideo information. However, another electronic device or a humanoperator may be used as an alternative to, or in addition to, thecomputer device. The lower and upper bands are bounded either by thebeamsplitter/filter optical device's 57 sensitivity or the camera's 11,12 sensitivity. Preferably, the lower band is 0.8 microns to 1.4 micron,and the upper band is 1.4 microns to 2.4 microns. However, othersomewhat different ranges may work as well.

[0050] The beamsplitter/filter optical device 57 provides at each pointin time, two co-registered frames in the upper and lower band at thehardware level of the system. Therefore, no time-consuming and generallycomplicated software to accomplish time registration is required like inthe embodiment described above with reference to FIG. 2B.

[0051] Further, a computer controlled near-infrared illumination sourcemay be added to the system to maintain optimal illumination levels inthe scene at all times. For example, a photometer may be used to sensescene illumination and provide a signal to initiate the need forcomputer adjustment of the illumination source.

[0052] As one can note here, a main application of the invention ispeople detection in vehicles. However, people detection can be used atsecurity points, alert areas, and so forth. An enhanced version ofsystem 10 may be used to actually identify people.

[0053] The spectrums in which cameras 11 and 12 function are within thereflected infrared portion 21 in FIG. 4, which shows the EM spectrum.Visible spectrum 22 is the spectral sensitivity of conventional cameras.Unfortunately, visible light cameras have noise levels that increaseduring poor environmental conditions such as bad weather, nighttime, anddirect sunlight. Some problems, such as nighttime viewing may beovercome with artificial lighting, which matches the visible spectrum ofthe camera, and which in vehicle occupant detection is a seriousdistraction to drivers. Another disadvantage is that a human face 13,which is the object of interest, does not have consistent qualitieswithin the visible range. Vehicle occupant faces appear dark or light,depending on the physiological characteristics of the occupant, and theintensity and incident angle of illumination.

[0054] The thermal infrared band 23 (3.0 to 5.0 and 8.0 to 14 microns)is associated with thermal properties of materials. The human body is ata temperature of 37 degrees C. This means that human faces have aconsistent light color in thermal infrared imaging, despite variousfacial colors, which is contrary to visible imaging.

[0055] The thermal property of the body provides a clear differentiatorfrom look-alike dummies. The thermal infrared sensor can function atnight without an external illuminator. One disadvantage of using thethermal infrared band 23 for occupant detection is that vehiclewindshield glass greatly attenuates infrared light transmission at 2.8microns and higher.

[0056]FIG. 5 reveals the transmittance characteristics of infrared lightbetween 0.4 and 2.8 microns for a clean vehicle windshield (curve 24)and a dirty windshield (curve 25). Beyond 2.8 microns of thermalinfrared bandwidth 23, the radiation transmittance characteristic ofwindshield glass is almost zero. The transmittance of a lightly tintedside window of a vehicle is good (50 to 85%), from 0.3 up to 2.8 micronsas revealed by curve 26 in FIG. 6. Between 2.8 and 4.3 microns, theradiation transmittance is about 20 percent for the side vehicle window.Beyond 4.3 microns the transmittance drops to nearly zero. However, thespectral behavior of the side window permits transmittance of somethermal radiation.

[0057] Curves 27 and 28 of FIG. 7 show the percentage of reflectance ofinfrared light for light and dark complexion Caucasian males,respectively. The reflectance is good between 0.6 and 1.4 microns. Above1.4 microns, the reflectance is significantly diminished. However, thedifference of reflectance of light and dark complexions are minimal.

[0058] In FIG. 8, curves 29 and 30 show skin reflectance for light anddark complexions, respectively, of Asian males. Curves 31 and 32 of FIG.9 show skin reflectance for light and dark complexions of black males.Even though the reflectance of light complexions is higher than those ofdark complexions; curves 27, 28, 29, 30, 31 and 32 of FIGS. 7-9,respectively, have similar shapes and all of them drop off at about 1.4microns. These reflectances show some variation for all complexions ofthe Caucasian, Asian, and black males, between 0.6 and 1.4 microns.

[0059] Curves 33 and 34 of FIG. 10 show the reflectance for more extremedifferences of light skin and dark skin, respectively. The reflectanceof light and dark skin are significant up to 1.4 microns. After 1.4microns, reflectance curves 33 and 34 for light and dark skin,respectively, become almost coincident and the resultant reflectancedrop below 20 percent. Thus, in the near-infrared bands of 1.4 andabove, the reflectance of detected humans of all kinds of skin shade,are about the same at wavelengths greater than 1.4 microns.

[0060] In FIG. 11, curves 35, 36, and 37 show the reflectance forcotton, wood, and polyamide respectively, to be significant not justbetween 0.6 and 1.4 microns, but beyond 1.4 microns. The insignificantdrop in reflectance after the 1.4 micron threshold point, is a basisthat shows a large contrast in reflectance between the human face andinanimate objects, such as upholstery, the dashboard, and fabrics in avehicle, which are background, and provide for easy detection of thehuman face in the range of 1.4 to 2.2 microns.

[0061] Consequently, there is a significant contrast, in reflectancebetween the images of a Caucasian male and a dummy head from a cameraoperating in the range between 1.4 and 2.2 microns. The image of thedummy is reflective and appears rather bright and the male human imageis dark and thus the resultant contrast between the two images is ratherstark. This person detection scheme is much superior to visible lightimaging, since the latter scheme reveals little or no contrast betweenthe Caucasian and dummy heads of like colors. In summary, it is easy todistinguish images of the human head from those of the dummy head in the1.4 to 2.2 micron range imagery, but not easy to distinguish the imagesof the respective heads from each other in the 0.8 to 1.4 micron rangeimagery.

[0062] The lower reflectivity of human skin for the 1.4 to 2.2 micronspectral range is explained by the spectral reflectance of distilledwater as shown by curve 38 of FIG. 12. There is a substantial drop inreflectance at about 1.4 microns. Beyond 1.4 microns, the water absorbssubstantial infrared radiation and appears in an image as a dark body.Since the composition of the human body consists of 70 percent waternaturally, its spectral response is similar to that of water. So camera12, operating in the 1.4 to 2.2 micron range, captures this unique humanbody differentiator. With the operating range of camera 12, one cansafely use during nighttime a matching near-infrared illumination source14 to improve the quality of the sensed image of face 13. This light isinvisible to humans, such as vehicle drivers, but also is harmless totheir eyes since the wavelength of illuminator 14 is above the safethreshold of 1.4 microns.

[0063] Also, since cameras 11 and 12 of system 10 operate at a lowerband than the mid-infrared band, glass penetration is not a problem andcameras 11 and 12 can easily detect through the frontal windshield of avehicle. Thus, speed requirements for cameras 11 and 12 are lessrestrictive. In an actual highway site, a zoom lens would be used.

[0064]FIG. 13 shows a layout of a near-infrared system 40 fordetermining the speed characteristics of the human detector. A vehicle41 may be assumed to be moving down a highway at a velocity v, as shownby vector 42, and be observed in a frontal view with a near-infraredcamera 11 or 12 at a distance d, as shown by line 43, and from a heighth, as shown by line 44. Only one of the cameras 11 and 12 is needed forthis evaluation, but it may be either one of them. Camera 11, 12 may bea Sensors Unlimited Inc. SU 320 equipped with a telephoto lens, aband-pass filter in the range 1.4 to x microns (where x>1.4 microns),and a polarizing filter to reduce the glare effect from the sunillumination during daytime.

[0065] During the daytime, system 40 uses the illumination of the sun.The objective is to determine if there is any appropriate geometricarrangement for camera 11, 12 so that the signal to noise (S/N) ratioand the camera speed are kept at acceptable levels even under adverseconditions. An acceptable (S/N) ratio is considered anything above 35.The speed quality is considered acceptable when the image smearing doesnot exceed the width of one pixel.

[0066] The first step in a radiometric computation is to determine theamount of radiation that falls upon the objects of interest such as theoccupants of vehicle 41. The spectral band considered is above the1.4-micron threshold point. Because of constraints due to the quantumefficiency of the camera SU-320 that was used in the actual experiments,one limits the spectral band in the range of 1.4 to 1.7 microns.Slightly modified things are in effect for the extended range of 1.4 to2.2 microns. The spectral irradiance of the sun (the illuminationsource) on a clear day at sea level is approximately I_(sunny)=0.008Watts/cm² in the 1.4 to 1.7 micron band range. In this computation,however, one considers the worst case scenario of an overcast day. Foran overcast day, the irradiance value is reduced by 10⁻³ thus givingirradiance at vehicle 41 of approximately $\begin{matrix}{I_{overcast} = {10^{- 3}*I_{sunny}}} \\{= {10^{- 3}*0.008}} \\{= {8\mu \quad {{Watts}/{{cm}^{2}.}}}}\end{matrix}$

[0067] The transmittance in this spectral range of windshield 45 ofvehicle 41 is approximately 0.4 resulting in an irradiance on thevehicle occupants of $\begin{matrix}{I_{occupant} = {0.4*I_{overcast}}} \\{= {0.4*8}} \\{= {3.2\quad \mu \quad {{Watts}/{{cm}^{2}.}}}}\end{matrix}$

[0068] The second step in a radiometric computation is to determine howmuch of the incident radiation on the objects of interest is reflectedback to the sensor (i.e., near-infrared camera 11, 12). The radianceinto a hemisphere assuming a reradiate oh 0.4 would be $\begin{matrix}{R_{occupant} = {0.4*{I_{occupant}/\pi}}} \\{= {0.4*{3.2/\pi}}} \\{= {{0.4\quad \mu \quad {{Watts}/{cm}^{2}}} - {{steradian}.}}}\end{matrix}$

[0069] This represents the reflected portion of the occupantirradiation. The occupant's body absorbs the rest. The reflectedradiation has to pass through windshield 45 and the camera 11, 12 lensto reach the near-infrared sensor array of camera 11, 12. One assumes a0.4 windshield transmittance, a f/2 camera lens (i.e., having a 14.32°cone angle) with 0.8 transmittance, a polarizer with 0.4 transmittance,and a band-pass filter with 0.6 transmittance. Then, the irradiance atthe sensor array of camera 11, 12 will be $\begin{matrix}{I_{camera} = {0.4*0.8*0.4*0.6*\pi*R_{occupant}*{\sin^{2}\left( {14.32{^\circ}} \right)}}} \\{= {0.4*0.8*0.4*0.6*\pi*0.4*{\sin^{2}\left( {14.32{^\circ}} \right)}}} \\{= {0.006\quad \mu \quad {{Watts}/{{cm}^{2}.}}}}\end{matrix}$

[0070] Camera 11, 12 has square pixels with a side of 37.5*10⁻⁴ cm or anarea $\begin{matrix}{A = {37.5*10^{- 4}*37.5*10^{- 4}}} \\{= {1.40*10^{- 5}{{cm}^{2}.}}}\end{matrix}$

[0071] Consequently, the radiant power on the camera 11, 12 pixel willbe $\begin{matrix}{P_{pixel} = {A*I_{camera}}} \\{= {1.4*10^{- 5}*0.006}} \\{= {0.084*10^{- 12}\quad {{Watts}.}}}\end{matrix}$

[0072] The camera's detectivity D* is D*=10¹² cm {square root}Hz/Watts.The noise equivalent power (NEP) is related to detectivity D*, pixelarea A, and electronic bandwidth Δf by the following equation:

NEP=(A/Δf)^(1/2) /D*.

[0073] The bandwidth Δf is determined by the exposure time of camera 11,12. The exposure time depends on vehicle 41 velocity 42, camera range40, and the camera 11, 12 field of view such that the images smear lessthan 1 pixel. Assuming vehicle 41 traveling at a speed of 65 mph, at adistance d 43 of 40 meters (m) away from camera 11, 12, and with a fieldof view of 1.6 m, the 320×240 pixel array of camera 11, 12 gives amaximum exposure time of 1 ms or a bandwidth of Δf=1 kHz. Substitutingthe values for A, Δf, and D* in the formula of NEP, one gets

NEP=1.18*10⁻¹³ Watts.

[0074] Therefore, the signal to noise ratio S/N will be

S/N=(P _(pixel) /NEP)=0.7.

[0075] In conclusion, assuming a worst case scenario (overcast day,dirty windshield, dark occupant skin) one determines that camera 11, 12,equipped with a f/2 lens, a 1.4 to 1.7 μm filter, and a polarizer, if itis positioned at a distance 43 of d=40 m from incoming car 41 and at aheight 44 of h=7 m at the specified distance 43, will achieve anacceptable smear of less than one pixel because the required exposuretime of 1 ms is within the camera's speed capabilities. The signal tonoise ratio (S/N) is 0.7. To boost the S/N ratio to a higher value onovercast days, one needs to employ an illumination source 14.Illumination source 14 will also be helpful during nighttime. If oneoperated in the visible spectrum, the use of an illuminator in the highoccupancy vehicle (HOV) lane would be prohibitive. Fortunately, in thiscase, the spectral signature of illuminator 14 for the 1.4 to 1.7 micronwave-band can be safely employed in the HOV lane.

[0076] Post processing includes a neural network that performs automaticvehicle occupant detection. The vehicle occupant detection approach isbased upon a fuzzy neural network algorithm. The perfect binary imageprovided by the fusion approach described above facilitates high correctdetection rates.

[0077] Further, with reference to several previous Figures, and alsoFIGS. 14-20, disguise detection systems and methods are describedwherein reflection properties of natural human anatomy (e.g., naturalskin and hair) in the upper band of the near-infrared spectrum are usedto provide for disguise detection, e.g., the detection of the presenceof artificial materials associated with the head of the human body.

[0078] The human skin has extremely low reflectance in the upper band ofthe near-infrared spectrum (i.e., 1.4 μm and greater in the nearinfrared spectrum) as previously described herein with reference toFIGS. 7-10. Such FIGS. 7-10 showed that human skin has a highreflectance between 0.6 and 1.4 microns. However, above 1.4 microns, thereflectance is significantly diminished. Since almost everything else ina typical scene has a higher reflectance in the upper band of thenear-infrared spectrum greater than 1.4 μm, there is sharp contrastbetween the human skin, e.g., face and neck, and the background.

[0079] Further, as shown by FIGS. 7-10, the skin reflectance property,i.e., that the reflectance of human skin above 1.4 microns in the upperband of the near infrared spectrum is significantly diminished, isuniversal across the human race, e.g., there is little difference insuch reflectance properties above 1.4 microns in the upper band of thenear infrared spectrum when comparing Caucasian, asian, and blackpersons. For example, FIG. 7 shows a drop-off in reflectance at or about1.4 microns for Caucasian males, FIG. 8 shows such a drop-off for asianmales, FIG. 9 shows such a drop-off for black males, and FIG. 10 showsthe drop-off for extreme differences of light skin and dark skin. Assuch, and as previously described herein, in the near-infrared band of1.4 and above, the reflectance of natural skin of detected humans of allkinds of skin shade are about the same at wavelengths greater than 1.4microns.

[0080] In contrast to the natural skin, human hair, i.e., natural hair,is highly reflective in the upper band of the near infrared spectrumabove 1.4. Such reflectance is also a property that is universal acrossthe human race. The highly reflective nature of human hair in the upperband of the near infrared spectrum above 1.4 microns is generally shownin FIG. 17. In FIG. 17, a reflectance diagram of natural human hair inat least a portion of the near-infrared spectrum is shown. Threeseparate reflectance measurements on a natural human hair specimenproduced the high reflectance properties shown in the diagram.

[0081] In contrast to the high reflectance of natural human hair, areflectance diagram of a human hair hairpiece (an artificial material aslater defined herein) is shown in FIG. 18. As shown therein, in theupper band of the near-infrared spectrum, reflectance is much lower thannatural hair. Even if true human hair is used to be fitted in a toupee,due to the chemical processing used in making a toupee, the reflectivecharacteristics are altered. Although the difference in reflectivitywhen comparing a true human hair wig to true natural human hair is muchsubtler, such reflectivity differences are still substantial and can beeasily captured.

[0082] In addition, the reflectance of various artificial materials,such as those used in disguises and as generally defined below (heavymake-up, artificial face parts, add-on hair, etc.) generally have areflectance that is significant beyond 1.4 microns. For example, asshown in FIG. 11, and previously described herein, the reflectanceproperties for cotton, wood, and polyamide do not drop significantly inreflectance after the 1.4 micron point. As such, there is a significantcontrast in reflectance properties between natural human skin and otherartificial materials, and also between natural human hair and artificialmaterials, in the upper band of the near infrared spectrum.

[0083] Yet further, as previously described herein, radiation in boththe upper and lower near-infrared bands can transmit through the windowglass of vehicles. Therefore, this is a definite advantage compared toboth the visible and the thermal infrared spectrums. As such, thepresent invention which uses the upper band of the near-infraredspectrum can detect disguised faces even within vehicles. Thetransmission characteristics through the window glass of vehicles isshown in the diagrams of FIGS. 5 and 6. As shown therein and asdescribed previously herein, FIG. 5 reveals the transmittancecharacteristics of infrared light between 0.4 and 2.8 microns for aclean vehicle windshield (curve 24) and a dirty windshield (curve 25).Beyond 2.8 microns at the beginning of the thermal infrared bandwidth,the radiation transmittance characteristic of windshield glass is almostzero. However, transmittance at less than 2.4 microns is very good. Thetransmittance of a lightly tinted side window of a vehicle is good (50to 85%), from 0.3 up to 2.8 microns as revealed by curve 26 in FIG. 6.As such, transmittance levels in the upper band of the near-infraredregion below 2.8 microns are very good.

[0084] The present invention uses at least a portion of the upper bandof the near infrared spectrum. As used herein, the upper band of thenear-infrared spectrum includes the range from 1.4 microns to 2.8microns. As previously indicated herein, at 2.8 microns thermal energybegins to appear. Preferably, according to the disguise detectionsystems and methods described herein, at least a portion of the upperband of the near-infrared spectrum within the range of 1.4 microns andabove is used. More preferably, at least a portion of the upper band ofthe near-infrared spectrum within the range of 1.4 microns to 2.4microns is used. Yet more preferably, at least a portion of the upperband of the near-infrared spectrum within the range of 1.4 microns to1.7 microns is used.

[0085] One skilled in the art will recognize that slightly shorter orlonger ranges can also yield acceptable detection results. For example,with respect to the ranges given above, a deviation from such wavelengthvalues which may produce acceptable detection results is contemplated tofall within the specified ranges.

[0086] Further, as used herein, artificial materials include anymaterials other than natural skin and/or natural hair, such as thoseitems or materials used for disguise purposes. For example, wigs,make-up materials, artificial nose pieces, etc., formed from one or moreartificial materials or inanimate objects such as polymers, fibers,etc., are referred to herein as artificial materials. Further,background objects are also referred to herein as artificial materials,e.g., a car behind a person, clothing of a person, etc.

[0087] Generally in disguise situations, an individual alters his or herfacial appearance through the addition/application of a fake nose,make-up, wig, artificial eyelashes, and the like. Professional actorsroutinely use this method for needs of their acting roles. A well donedisguise by this technique is very difficult or impossible to bedetected in the visible spectrum. Generally, the face has been touchedwith a make-up material to integrate smoothly the fake nose. Althoughdisguises are usually very simplistic, the facial appearance of theperson changes substantially. As such, there is no way to visuallydetect the deception without prior knowledge.

[0088] Detection systems and methods described herein are able to detectdisguises due to the fact that any artificial materials applied to thehead of the human, e.g., facial skin or scalp, alters to variousdetectable degrees the respective unique infrared signatures of suchhumans, particularly in the upper band of the near-infrared spectrum.Therefore, although disguise configurations can easily fool the eye inthe visible spectrum, such disguises are immediately apparent in theupper band of the near-infrared spectrum.

[0089] The reflectance characteristics of various artificial materials,and also natural hair and natural skin of the human body, as describedabove can be more clearly understood through the display of suchreflectance characteristics as shown or described further below withreference to FIGS. 14A-B and FIGS. 15A-B. FIG. 14A shows an undisguisedhuman head 102 in a visible spectrum. The human head 102 includes afacial portion 114 of natural skin and natural human hair 112 includinga beard, a mustache, eyebrows, and scalp hair.

[0090]FIG. 14B shows the undisguised human head 102 in the upper band ofthe near-infrared spectrum based on the reflectance properties in thescene. In the upper band of the near-infrared spectrum, the naturalhuman skin of the facial portion 114 has a dark appearance due to itslow reflectance characteristics. On the other hand, the facial hair 112including the beard, mustache, eyebrows, and scalp hair has a brightappearance due to its highly reflective nature in the upper band of thenear-infrared spectrum. As such, the undisguised person has a uniquenear-infrared signature due to the reflectance characteristics of theperson's natural hair and natural skin in the upper band of thenear-infrared spectrum. As previously described herein, suchcharacteristics are universal for the entire human species.

[0091]FIG. 15A shows a disguised human head 106 in the visible spectrum.The disguised human head 106 includes a facial portion 116 havingnatural skin but with a fake nose 117 fitted thereon and touched up bymake-up. Further, the disguised human head 106 includes a wig 118covering the scalp of the human head and a fake beard 108. Natural haircomponents 119 include the eyebrows and mustache.

[0092] Such a disguise is not detectable in the visible spectrum, asshown in FIG. 15A. However, the artificial materials alter radically thesignature of the person's head in the upper band of the near infraredspectrum. As a result, facial skin appears very bright in the area ofthe fake nose 117, and is an obvious abnormality in the uppernear-infrared band as shown in FIG. 15B. In contrast, the artificialhair wig and beard has much lower reflectivity than natural human hairin the upper band of the near-infrared spectrum. As a result, theartificial hair 108, 118 of the human head 106 appears very dark in theimage, due to its low reflectivity, and the natural hair, i.e., themustache and eyebrows 119, appear bright.

[0093] Such abnormalities are readily detectable, as can be seen in FIG.15B. In FIG. 15B, the human head 106 shows the abnormal dark hair 118covering the scalp and abnormal dark beard 108. If such hair werenatural hair, it would have a similar brightness as that shown in FIG.14B and like the natural hair 119 including the eyebrows and mustache.Likewise, further, the artificial materials used to form the fake noise117 are clearly abnormal due to their high reflectivity compared to theother natural skin facial portion 116.

[0094] As described above, it can be readily seen that an imaging systembased on the reflectivity in the upper band of the near-infraredspectrum provides advantageous disguise detecting ability. Such a systemand method is based on various reflectivity characteristics in the upperband of the near-infrared spectrum. Such characteristics include atleast: that the human skin has very low reflectivity in the upper bandof the near-infrared spectrum and always ranks amongst the darkestobjects in the scene; that artificial materials, e.g., facial disguisematerials, feature high reflectivity in the upper band of thenear-infrared spectrum and always rank among the brightest objects inthe scene and, as such, when they are applied to natural skin and hairof the human head, they alter totally its phenomenology and facilitateeasy detection in the imagery by a human observer or a machine visionsystem; that the natural human hair has high reflectivity in the upperband of the near infrared spectrum and always ranks amongst thebrightest objects in the scene; and further that artificial hair or eventrue human hair wigs feature low reflectivity in the upper band andalways rank amongst the darkest objects in the scene and, as such, whenthey are applied to the scalp or to the face of a human head, they altertotally the expected phenomenology and facilitate easy detection in theimagery by a human observer or a machine vision system.

[0095]FIG. 16 shows one illustrative embodiment of a disguise detectionsystem 130 according to the present invention. The disguise detectionsystem 130 includes circuitry 132, an upper near-infrared camera 134, aphotometer 140, an upper near-infrared illuminator 136, and acomputer-controlled power supply 138. The upper near-infrared camera 134may be a camera like that previously described herein with reference toFIGS. 1 and 2. The camera is sensitive to at least a portion of theupper band of the near-infrared spectrum, preferably in the range of 1.4microns and above, more preferably in the range of 1.4 microns to 2.4microns, and even more preferably in the range of 1.4 microns to 1.7microns in the upper band of the near-infrared spectrum. Such camerasgenerally have a sensing array, for example, an array of pixels thatprovide signals based on the light captured thereby, as is readily knownto those skilled in the art. The pixel signals representative of theimage based on the light captured is provided to circuitry 132. Forexample, the upper near-infrared camera may be a camera available fromSensors Unlimited, under the trade designation SU-320.

[0096] Preferably, circuitry 132 includes a computer system 133 operableto execute software to provide a user with information as to thepresence of an artificial material associated with the head of the humanbody based on the detected reflection in the upper band of thenear-infrared spectrum. Although the circuitry 132 may be implementedusing software executable using a computer apparatus, other specializedhardware may also provide the functionality required to provide a userwith information as to the presence of an artificial material associatedwith the head of the human body, e.g., information concerning adisguise. As such, the term circuitry as used herein includes not onlyspecialized hardware, but may also include circuitry such as processorscapable of executing various software processes.

[0097] For example, the computer system 133 may be any fixed or mobilecomputer system, e.g., a personal computer or a minicomputer. The exactconfiguration of the computer system is not limiting and most any devicecapable of providing suitable computing capabilities may be usedaccording to the present invention. Further, various peripheral devices,such as a computer display, a mouse, a keyboard, memory, printer, etc.,are contemplated to be used in combination with a processing apparatusof the system.

[0098] The detector or photometer 140 is operable to detect anillumination level proximate the head of the human body which is in thescene being captured by camera 134. The photometer 140 providesinformation to the computer system 133 based on the detectedillumination level. The computer system 133 is operable to control theupper near-infrared illuminator 136 which is an illumination sourcematched to the upper band of the near-infrared spectrum used to performthe method according to the present invention. The upper near-infraredilluminator 136 is positioned to illuminate at least a portion of thehead of the human body, e.g., the scene in which the human body islocated. The circuitry 132, e.g., the computer system 133, is operableto control the upper near-infrared illuminator 136 based on the detectedillumination level provided by the photometer 136 to maintain a desiredillumination level of the head of the human body, e.g., illumination ofthe scene in which the human body is located. In one embodiment,software of computer system 133 may be used to automatically adjust theillumination level of the upper band near-infrared illuminator 136 tomaintain an optimal illumination level in the scene at all times. Theadjustment of the illumination level is based on the readings fromphotometer 140 and may be realized through power supply 138.

[0099] The illumination assists in the production of a high qualityimaging signal from the camera 134, even during overcast days and atnight. Such illumination can be used because the scene can be safelyilluminated with such eye-safe near-infrared illuminators. Also, sincethe eye is not sensitive to the near-infrared spectrum, the systemremains stealth at all times. Any suitable photometer and illuminatormay be used to provide for suitable illumination of the scene in whichthe human body being captured by the camera 134 is located.

[0100] Both the camera 134 and illuminator 137 may be moved by anysuitable structure represented by arrows 135 and 137, respectively, suchthat a larger field of view may be possible. For example, the camera 134may be moveably mounted for capturing images in a 180° field of view,and likewise illuminator 136 may be moved so as to provide adequateillumination to achieve an imaging signal from camera 134 of sufficientquality to perform disguise detection.

[0101] Using a detection system such as, for example, the disguisedetection system 130 of FIG. 16, various methods of determining thepresence of an artificial material associated with the head of the humanbody based on the detected reflection may be performed. Two illustrativeembodiments of such methods are shown in FIGS. 19 and 20. The method 150shown in FIG. 19 provides for detection by a human observer, such as byviewing displayed images as shown in FIGS. 14 and 15. FIG. 20 shows anillustrative embodiment of a method 160 which includes additionalprocessing of the data to provide additional information to the userother than just displayed images, e.g., such as information that may beprovided using a machine vision system, or other information instead ofdisplayed images.

[0102] The method 150, illustratively shown in FIG. 19, will bedescribed with reference to the displayed images of FIGS. 15A and 15B.The method 150 includes initiating the disguise detection system (block152). Upon initiating the disguise detection system (block 152), imagedata representative of the reflection in at least a portion of the upperband of the near-infrared spectrum is captured by camera 134. Thereflection data from camera 134, e.g., pixel signal data, is provided tothe circuitry 132, e.g., a computer system 133, which may operate on thedata using a thresholding process (block 154) so as to manipulate thedata and to provide an image to be displayed for viewing by a user(block 156).

[0103] Various thresholding techniques have been used as is readilyknown to those skilled in the art. Any suitable thresholding processthat provides for acceptable segmentation of dark and light regions maybe used according to the present invention. In general, suchthresholding processes compare the data representative of the reflectionto one or more thresholding values. Such values may be based on avariety of factors, such as the reflection characteristics of naturalskin, of natural hair, etc. For example, a thresholding processdescribed in the article entitled “A Threshold Selection Method fromGray-Level Histograms” by Otsu, IEEE Transactions on Systems, Man AndCybernetics, Vol. SMC-9, No. 1, January 1979, may be used according tothe present invention. The thresholding process generally involves anon-parametric and unsupervised method of threshold selection. Anoptimal threshold is selected so as to maximize the separability of theresultant classes in gray levels. The algorithm utilizes only thezeroth-order and the first-order cumulative moments of the gray levelhistogram. The speed of the system, in part because of the thresholdingprocess, can provide real time images to the user.

[0104] The user when presented with the displayed image such as shown inFIGS. 14B and 15B (block 156) can then view any abnormal characteristicsof the image, e.g., the bright nose feature 117 representative of a fakenose, the dark facial hair features 108 and 118 which are abnormallydark compared to natural hair, etc. as shown in FIG. 15B. Upon detectionof such abnormalities by the user, appropriate action may be taken. Suchaction may include the sounding of an alarm, direct contact with thedisguised individual, etc.

[0105] In such a method 150, there may be a direct correlation betweenthe level of reflectance and the brightness of features like thatrepresented in FIG. 15B, e.g., high level of reflectance being shown asbright feature. However, additional processing in conjunction with thethresholding process may be used to display detected artificialmaterials in any differentiating manner. For example, the skin 116 mayactually be represented as a first shade and the nose being abnormallyrepresented as a different shade easily recognized by a user. Forexample, the brightness of the portions of the image may be reversedfrom that shown in FIG. 15, e.g., the fake nose is dark and the skin isbrighter than the fake nose.

[0106] The method 160, illustratively shown in FIG. 20, includesinitiating the disguise detection system (block 162). Once the data hasbeen captured by camera 134 and provided to the computer system 133, thereflectance data, e.g., pixel signal data, from camera 134 is analyzed(block 164). The data may be analyzed in one or more different manners.

[0107] In one illustrative embodiment, for example, the data may becompared to one or more threshold levels. The one or more thresholdlevels (block 166) provided for comparison to the reflection data may bethreshold levels based simply on the natural skin and natural hairreflectance characteristics. However, such threshold levels may also bebased on a plurality of reflectance properties of the artificialmaterials themselves used in disguises. As such, the reflectancecharacteristics of a number of known disguise materials can be mappedinto a multi-level thresholding algorithm. With use of such amulti-level thresholding algorithm, not only can detection of disguisesbe attainable, the detection and existence of specific materials used inthe disguises may be obtained by the detection of reflectance andcomparison using the multi-level thresholding algorithm.

[0108] For example, reflectance measurements in the upper band of thenear-infrared spectrum may be gathered for all known possible disguisematerials used in the trade. A direct mapping between differentartificial materials and thresholding levels corresponding to aparticular reflectance characteristic can be performed. Likewise,various other disguise situations may be mapped. For example, a list offacial images featuring just a single disguise item, e.g., a fakemustache only or a heavy make-up only, may be mapped. As will berecognized, the list of disguises which may be mapped is unlimited,however, a multi-level thresholding scheme can be developed that may beused to identify any number of various disguises. As such, with the useof a multi-level thresholding scheme, the identification of one or moreartificial materials associated with the head of the human body can beidentified and the user alerted to the presence of such artificialmaterials (block 168). For example, upon comparing the reflection datafrom the camera 134, with use of computer system 133, to such amulti-level threshold reference map, an alert may be presented to theuser indicating the presence of an artificial material associated withthe head (block 168). The user may then take appropriate action.

[0109] The user may be alerted in any number of ways. For example,information may be displayed, a silent alarm may be used, an audioalarm, a tactile alarm, etc. Such information displayed may include, forexample, an alarm mechanism, information as to the disguised person, thedisguised materials being used, and/or the level of security riskinvolved with the disguised person.

[0110] It will be recognized that various methods and systems describedherein may be used in combination and/or such methods and systems may beused in combination with other detection systems. For example, in oneillustrative embodiment of such a combined system according to thepresent invention, reflections from a scene in at least a portion of oneband of the near-infrared spectrum may be detected. The presence of thehead of the human body in a scene may be determined based on thedetected reflection in the portion of the one band of the near-infraredspectrum, e.g., segmentation of the head from the background of a scene.Thereafter, the reflection from at least one portion of the head of thehuman body in at least a portion of an upper band of the near-infraredspectrum may be detected to determine the presence of an artificialmaterial associated with the head of the human body based on suchreflection.

[0111] For example, such a combination system and method may beimplemented using the two camera system previously described herein. Forexample, the dual band near-infrared method may be used for facedetection for the location of a head. Thereafter, the disguise detectionmethod may be used to determine the presence of an artificial material.

[0112] Further, for example, in another embodiment of such a combinationsystem and method, the head may be determined to be present by detectingthe reflection from a scene in at least a portion of the upper band ofthe near-infrared spectrum. For example, the upper band of thenear-infrared spectrum within the range of 1.4 μm to 2.2 μm may be usedto determine the presence of the human head such as described previouslyherein, e.g., wherein a dummy head is differentiated from the human heador a human head is differentiated form a background. Further,thereafter, it may be determined whether the human head is disguisedalso using the upper band of the near-infrared spectrum, as previouslydescribed herein.

[0113] Such methods and systems may be used in combination with othersystems and methods such as those that employ thermal infrareddetection. Thermal infrared detection may be used for detecting cosmeticsurgery disguises. Such cosmetic surgery disguises may not be detectableby the disguise detection process using the upper band of thenear-infrared spectrum, as previously described herein. Likewise,visible spectrum systems may be used in combination with the previouslydescribed methods and systems herein so as to enhance detectioncapabilities.

[0114] All patents and references cited herein are incorporated in theirentirety as if each were incorporated separately. Although the inventionhas been described with particular reference to the preferredembodiments thereof, variations and modifications of the presentinvention can be made within a contemplated scope of the claims, as isreadily known to one skilled in the art.

What is claimed is:
 1. A method for use in detection of a persondisguised with one or more artificial materials, the method comprising:detecting reflection from at least one portion of a head of a human bodyin at least a portion of an upper band of the near infrared spectrum;and determining the presence of an artificial material associated withthe head of the human body based on the detected reflection.
 2. Themethod of claim 1, wherein the at least a portion of the upper band ofthe near infrared spectrum is at least a portion within the range of 1.4μm and above in upper band of the near infrared spectrum.
 3. The methodof claim 2, wherein the at least a portion of the upper band of the nearinfrared spectrum is at least a portion within the range of 1.4 μm to2.4 μm in the upper band of the near infrared spectrum.
 4. The method ofclaim 3, wherein the at least a portion of the upper band of the nearinfrared spectrum is at least a portion within the range of 1.4 μm to1.7 μm in the upper band of the near infrared spectrum.
 5. The method ofclaim 1, wherein detecting reflection comprises detecting reflectionfrom at least a skin portion of the head of the human body.
 6. Themethod of claim 1, wherein detecting reflection comprises detectingreflection from at least a hair portion of the head of the human body.7. The method of claim 1, wherein determining the presence of anartificial material associated with the head of the human body comprisesdisplaying to a user a representation of the detected reflection of theat least one portion of the head of the human body.
 8. The method ofclaim 1, wherein determining the presence of an artificial materialassociated with the head of the human body comprises: generating datarepresentative of the detected reflection; and comparing the data to atleast one threshold reference reflection level.
 9. The method of claim8, wherein generating data representative of the detected reflectioncomprises focusing the reflection on a pixel array that is sensitive tothe at least a portion of the upper band of the near infrared spectrum,and generating a signal representative of the spectral power for each ofa plurality of pixels of the pixel array to be used for the comparisonto the at least one threshold reference reflection level.
 10. The methodof claim 8, wherein the at least one threshold reference reflectionlevel is based on a level of reflection of the one or more artificialmaterials.
 11. The method of claim 10, wherein the at least onethreshold reference reflection level is a plurality of referencereflection levels corresponding to a plurality of artificial materials,and further wherein the method comprises identifying one or more of theartificial materials associated with the head of the human body.
 12. Themethod of claim 8, wherein the at least one threshold referencereflection level is based on a level of reflection of natural skin ofthe human body.
 13. The method of claim 8, wherein the at least onethreshold reference reflection level is based on a level of reflectionof natural hair of the human body.
 14. The method of claim 1, whereinthe method further comprises illuminating the at least a portion of thehead of the human body using an illumination source matched to the atleast a portion of the upper band of the near infrared spectrum.
 15. Themethod of claim 14, wherein the method further comprises: detecting anillumination level proximate the head of the human body; and controllingthe illumination source based on the detected illumination level tomaintain a desired illumination level on the head of the human body. 16.A disguised person detection system comprising: a detector apparatusoperable to detect reflection from at least a portion of a head of ahuman body in at least a portion of an upper band of the near infraredspectrum; and an indication apparatus operable to provide a user withinformation as to the presence of an artificial material associated withthe head of the human body based on the detected reflection.
 17. Thesystem of claim 16, wherein the at least a portion of the upper band ofthe near infrared spectrum is at least a portion within the range of 1.4μm and above in the upper band of the near infrared spectrum.
 18. Thesystem of claim 17, wherein the at least a portion of the upper band ofthe near infrared spectrum is at least a portion within the range of 1.4μm to 2.4 μm in the upper band of the near infrared spectrum.
 19. Thesystem of claim 18, wherein the at least a portion of the upper band ofthe near infrared spectrum is at least a portion within the range of 1.4μm to 1.7 μm in the upper band of the near infrared spectrum.
 20. Thesystem of claim 16, wherein the indication apparatus comprises a displayoperable to provide a representation of the detected reflection of theat least the portion of the head of the human body.
 21. The system ofclaim 16, wherein the system further comprises a display operable toprovide a representation of the detected reflection of the at least theportion of the head of the human body for use in presenting theinformation as to the presence of an artificial material associated withhe head of the human body.
 22. The system of claim 16, wherein thedetector apparatus comprises one or more pixels sensitive to the atleast a portion of the upper band of the near infrared spectrum andoperable to provide information representative of the detectedreflection from the at least the portion of the head of the human body,and further wherein the indication apparatus comprises circuitryoperable to compare the information representative of the detectedreflection to at least one threshold reference reflection level.
 23. Thesystem of claim 22, wherein the at least one threshold referencereflection level is based on a level of reflection of the one or moreartificial materials.
 24. The system of claim 23, wherein the at leastone threshold reference reflection level is a plurality of referencereflection levels corresponding to a plurality of artificial materials,and further wherein the circuitry of the indication apparatus isoperable for use in identifying one or more of the artificial materialsassociated with the head of the human body.
 25. The system of claim 22,wherein the at least one threshold reference reflection level is basedon a level of reflection of natural skin of the human body.
 26. Thesystem of claim 22, wherein the at least one threshold referencereflection level is based on a level of reflection of natural hair ofthe human body.
 27. The system of claim 16, wherein the system furthercomprises an illumination source matched to the at least a portion ofthe upper band of the near infrared spectrum positioned to illuminatethe at least the portion of the head of the human body.
 28. The systemof claim 27, wherein the system further comprises a detector operable todetect an illumination level proximate the head of the human body, andfurther wherein the indication apparatus comprises circuitry operable tocontrol the illumination source based on the detected illumination levelto maintain a desired illumination level of the head of the human body.29. A detection method comprising: detecting reflection from a scene inat least a portion of one band of the near infrared spectrum;determining the presence of a head of a human body in the scene based onthe detected reflection in the at least a portion of the one band of thenear infrared spectrum; detecting reflection from at least one portionof the head of the human body in at least a portion of an upper band ofthe near infrared spectrum to determine the presence of an artificialmaterial associated with the head of the human body based on thedetected reflection from at least one portion of the head of the humanbody.
 30. The method of claim 29, wherein detecting reflection from ascene in at least a portion of one band of the near infrared spectrumcomprises detecting reflection from the scene in at least a portion of alower band of the near infrared spectrum and from the scene in at leasta portion of an upper band of the near infrared spectrum.
 31. The methodof claim 30, wherein the at least a portion of the lower band of thenear infrared spectrum is at least a portion within the range of 0.8 ∥mto 1.4 μm in the lower band of the near infrared spectrum, and furtherwherein the at least a portion of the upper band of the near infraredspectrum is at least a portion within the range of 1.4 μm to 2.2 μm inthe upper band of the near infrared spectrum.
 32. The method of claim29, wherein detecting reflection from a scene in at least a portion ofone band of the near infrared spectrum comprises detecting reflectionfrom the scene in at least a portion of the upper band of the nearinfrared spectrum.
 33. The method of claim 32, wherein the at least aportion of the upper band of the near infrared spectrum is at least aportion within the range of 1.4 μm to 2.2 μm in the upper band of thenear infrared spectrum.
 34. The method of claim 29, wherein detectingreflection from at least one portion of a head of a human body in atleast a portion of an upper band of the near infrared spectrum comprisesdetecting reflection from at least one portion of a head of a human bodyin at least a portion within the range of 1.4 μm to 2.2 μm in the upperband of the near infrared spectrum.
 35. The method of claim 29, whereindetecting reflection from at least one portion of a head of a human bodycomprises detecting reflection from at least a skin portion of the headof the human body.
 36. The method of claim 29, wherein detectingreflection from at least one portion of a head of a human body comprisesdetecting reflection from at least a hair portion of the head of thehuman body.
 37. The method of claim 34, wherein to determine thepresence of an artificial material associated with the head of the humanbody a representation of the detected reflection of the at least oneportion of the head of the human body is displayed to a user.
 38. Adetection system for use in detecting a human in a scene, the detectionsystem comprising: a first camera sensitive to a first band ofwavelengths within a reflected infrared radiation range and operable toprovide one or more frames of a first image output representative of thescene; a second camera sensitive to a second band of wavelengths withinthe reflected infrared radiation range and operable to provide one ormore frames of a second image output representative of the scene; anoptical device positioned to direct light reflected from the scene in atleast the first band of wavelengths to the first camera and to directlight reflected from the scene in at least the second band ofwavelengths to the second camera, wherein the one or more frames of thefirst image output are co-registered in time with the one or more framesof the second image output; and a processing apparatus operable todetect a human in the scene based on the first and second image outputs.39. The system of claim 38, wherein the optical device comprises acombination beamsplitter and filter.
 40. The system of claim 39, whereinthe optical device is an optical component having a coating thereon thatdirects light with wavelengths below about 1.4 microns to the firstcamera and light with wavelengths above about 1.4 microns to the secondcamera.
 41. The system of claim 38, wherein the processing apparatus isoperable to fuse spectral power of the pixels of the first image outputwith spectral power of corresponding pixels of the second image outputto provide a fused image output having an increased contrast between ahuman and a background in the scene.
 42. The system of claim 41, whereinthe processing apparatus is further operable to segment the human fromthe scene by comparing the spectral power of each pixel of the fusedimage output to one or more threshold values.
 43. The system of claim38, wherein a difference in reflectance for human skin in the first bandof wavelengths relative to the second band of wavelengths is greaterthan a difference in reflectance for objects other than human skin inthe first band of wavelengths relative to the second band ofwavelengths.
 44. The system of claim 38, wherein the processingapparatus is further operable to perform a weighted differencecalculation of spectral power of the pixels of the first image outputwith spectral power of corresponding pixels of the second image outputresulting in a weighted difference output for the pixels.
 45. The systemof claim 44, wherein the processing apparatus is further operable tocompare the weighted difference output for the pixels to one or morethreshold values to differentiate pixels representative of human skinfrom pixels representative of objects other than human skin.
 46. Thesystem of claim 38, wherein said first and second cameras have the samefields-of-view.
 47. A detection system comprising: first camera meansfor sensing radiation of a scene within a first band of wavelengths in areflected infrared radiation range and operable to provide one or moreframes of a first image output representative of the scene; secondcamera means for sensing radiation of the scene within a second band ofwavelengths in the reflected infrared radiation range and operable toprovide one or more frames of a second image output representative ofthe scene; optical device means positioned for directing light reflectedfrom the scene in at least the first band of wavelengths to the firstcamera means and for directing light reflected from the scene in atleast the second band of wavelengths to the second camera means suchthat one or more frames of the first image output are co-registered intime with one or more frames of the second image output; and processingmeans for detecting a human in the scene based on the first and secondimage outputs.
 48. The system of claim 47, wherein the processing meanscomprises: fusing means connected to said first and second camera meansfor fusing spectral powers P(i,j)₁ of pixels (i,j)₁ from said firstcamera means with spectral powers P(i,j)₂ of corresponding pixels (i,j)₂from said second camera means, resulting in fused spectral powersP(i,j)_(f); and thresholding means, connected to said fusing means, forthresholding fused spectral powers P(i,j)_(f) from said fusing means,resulting in threshold spectral powers P(i,j)_(t); and wherein: thescene is focused by said first camera means on a first sensing arrayhaving m×n pixels; the scene is focused by said second camera means on asecond sensing array having m×n pixels; each pixel is located at ith rowand jth column; 0≦i≦m; and 0<j≦n.
 49. The system of claim 48, furthercomprising indicating means for displaying a segmented image of thescene.
 50. The system of claim 49, wherein: P(i,j)_(f) =P(i,j)₁−C*P(i,j)₂; and C is a constant determined according to a lightingcondition of the scene.
 51. The system of claim 50, wherein: P(i,j)₁ =V₁ if P(i,j)_(f) >T; P(i,j)_(t) =V ₂ if P(i,j)_(f) <T; V₁ is a firstvalue; V₂ is a second value; and T is a threshold value, wherein T isdetermined by a spectral power distribution of fused pixels (i,j)_(f).52. The system of claim 47, wherein a wavelength between the first andsecond bands of wavelengths is about 1.4 microns.
 53. The system ofclaim 47, wherein: the first band of wavelengths is between about 0.8and 1.4 microns; and the second band of wavelengths is between about 1.4microns and 2.2 microns.
 54. A method for detecting humans, comprising:focusing a scene on a first m x n pixel array that is sensitive to lightof a first bandwidth within a reflected infrared radiation rangeresulting in one or more frames of a first image output representativeof the scene and on a second m×n pixel array that is sensitive to lightof a second bandwidth within the reflected infrared radiation rangeresulting in one or more frames of a second image output representativeof the scene; co-registering one or more frames of the first imageoutput with one or more frames of the second image output, whereinco-registering the frames comprises using an optical device to directlight reflected from the scene in at least the first bandwidth to thefirst m×n pixel array at each of a plurality of points in time anddirecting light reflected from the scene in at least the secondbandwidth to the second m×n pixel array at each of the plurality ofpoints in time; and using the first and second image outputs to detect ahuman in the scene.
 55. The method of claim 54, wherein using the firstand second image outputs to detect a human in the scene comprises fusingspectral power of the pixels of the first image output with spectralpower of corresponding pixels of the second image output to provide afused image output having an increased contrast between a human and abackground in the scene.
 56. The method of claim 55, wherein using thefirst and second image outputs to detect a human in the scene furthercomprises segmenting the human from the scene by comparing the spectralpower of each pixel of the fused image output to one or more thresholdvalues.
 57. The method of claim 56, wherein the method further comprisesdisplaying a segmented image.
 58. The method of claim 54, wherein awavelength between the first and second bandwidths is about 1.4 microns.59. The method of claim 54, wherein the first bandwidth is between about0.8 and 1.4 microns and the second bandwidth is between about 1.4microns and 2.2 microns.
 60. The method of claim 54, wherein adifference in reflectance for human skin in the first bandwidth relativeto the second bandwidth is greater than a difference in reflectance forobjects other than human skin in the first bandwidth relative to thesecond bandwidth.
 61. The method of claim 54, wherein using the firstand second image outputs to detect a human in the scene comprisesperforming a weighted difference calculation of spectral power of thepixels of the first image output with spectral power of correspondingpixels of the second image output resulting in a weighted differenceoutput for the pixels.
 62. The method of claim 61, wherein using thefirst and second image outputs to detect a human in the scene furthercomprises comparing the weighted difference output for the pixels to oneor more threshold values to differentiate pixels representative of humanskin from pixels representative of objects other than human skin. 63.The method of claim 54, wherein using the first and second image outputsto detect a human in the scene comprises: fusing a spectral powerP(i,j)₁ of each pixel of the first m×n pixel array with a spectral powerP(i,j)₂ of each corresponding pixel of the second m×n pixel array, toresult in a spectral power P(i,j)_(f) of a fused pixel, respectively;thresholding the spectral power P(i,j)_(f) of each fused pixel into afirst value if the spectral power is greater than a threshold value; andthresholding the spectral power P(i,j)_(f) of each fused pixel into asecond value if the spectral power is less than the threshold value;wherein: 0<i≦m; and 0<j≦n.
 64. The method of claim 63, wherein:P(i,j)_(f) =P(i,j)₁ −C*P(i,j)₂; and C is a constant dependent upon alighting condition of the scene.
 65. The method of claim 64, wherein:P(i,j)_(t) =V ₁ if P(i,j)_(f) >T; P(i,j)_(t) =V ₂ if P(i,j)_(f) <T; V₁is a first value; V₂ is a second value; and T is a threshold valuedependent upon a distribution of spectral powers P(i,j)_(f) of the fusedpixels.